We discovered a systemic problem with our whole-room indirect calorimetry suites (commissioned in August 2008). During the winter of this year, we detected significant artifacts in all three chambers that lead to unstable performances. After rigorous testing, we traced the issue to extreme low relative humidity of the building supply air as it introduced high differential partial pressure (of water vapor) between the chamber and reference air. We engaged with building engineers and officials from Office of Facility Management, Office of Research Facilities, and the Clinical Center. We confirmed our findings of low humidity and are currently working towards a three-prong approach to rectify the issue: (1) tighter humidity control of the Metabolic Unit supply air to provide a more stable environment by the OFM, (2) use the Clinical Center medical air as supply air for the calorimetry suites, and (3) revamp the calorimetry air sample and condition equipment, calibration gas mixing, and analyzer upgrades. With the strong support from NIDDK leadership and Clinical Center, we are making steady progress in these critical renovations. Research findings: In 25 young and normal-weight healthy volunteers, Dr. Celi and his colleagues have found that a 12-hr environmental temperature change (from 24 to 19 C) produced a 6% increase in resting energy expenditure as measured by our metabolic suites. This increase was likely a result of the activation of brown adipose tissue via the sympathetic nervous system, but less of an influence by the thyroid hormone. While expanded studies are underway to study obese and elderly individuals and to further quantify the brown adipose tissue activity by FDG-PET imaging, we have published the current findings. We are continuing our intra/extramural collaboration project with Dr. Naji Abumrad from Vanderbilt University to study the changes in energy metabolism, protein turnover, insulin action, and associated weight loss before and after Roux-en-Y gastric bypass surgery. The Vanderbilt study has stopped new recruitment but we following up the patients that we studied on whole-body metabolism during rapid weight loss. We have published a manuscript in Obesity recently. Services rendered (FY09 activities): 24-hr energy expenditure by whole-room respiratory chambers (299), resting energy expenditure by metabolic carts (364), exercise and physical function testing (144), body composition (581 Bod Pod measurements, 388 iDXA scans), objective physical activity monitoring (588), food-array experimental dinning (146), muscle biopsies (28), subcutaneous fat biopsies (79), and Health and Physical Exams (75). All activities are significantly up from FY08, despite of the humidity issue with the metabolic chambers.